A disk is known for digital signal recording which is a small-sized digital audio disk having a diameter of about 12 cm, which is called a compact disk (CD). Recently, however, there has been developed a disk of the same diameter as the compact disk on which in addition to a PCM (pulse code modulation) signal, an FM-modulated video signal and a PCM signal are recorded in a superimposed state (hereinafter, referred to as a composite disk).
In the case of such a composite disk as described above, information is recorded, for example, in two regions in such a manner that PCM-modulated audio information is recorded in a first region located at the inner circumferential side of the disk and an FM-modulated video signal and a PCM-modulated audio signal are recorded in a superimposed state in a second region located at the outer circumference outside a predetermined radial position of the disk.
In such a compact disk, index codes related to recorded contents, for example, information representing the number of recorded music, the total absolute time, the playing time for every music piece, and so on, are recorded in a read-in area in order to perform special reproduction such as search, skip, etc. Accordingly, in reproduction, the information recorded in the read-in area is read out prior to reproduction of the program information. This applies also to a composite disk in order to perform such special reproduction.
In the case of a composite disk, however, the recording region is divided into two divided recording regions so that a read-in area is provided in each of the divided recording regions and different information is recorded in the divided recording regions and therefore there exist two kinds of index codes corresponding to the divided recording regions. In order to perform special reproduction from both of the two divided regions, it is necessary to record each of the two kinds of index codes not only in the read-in area of the divided recording region corresponding to the index code in question but in the read-in area of the other divided recording region corresponding to the other index code. Those index codes recorded in those two read-in areas are read out prior to reproduction of program information and stored in a memory for every region corresponding to the index code. Accordingly, in storing those read-out index codes, it is desired to use the memory efficiently